Multichannel stochastic gradient method for adaptive equalization in uplink asynchronous DS/CDMA

The paper addresses the problem of channel equalization in asynchronous uplink DS/CDMA systems. An MMSE equalizer is derived based on our proposed channel estimation algorithm (Sirbu, M. and Koivunen, V., Proc. IEEE Int. Conf. on DSP, 2002). For channel estimation, there is no need for knowledge of the propagation delays, whereas for despreading purposes only the chip period multiple of the propagation delays has to be estimated. The proposed scheme processes all user signals simultaneously. The performance is studied based on simulations in non-stationary channel conditions.